I've come a cross an issue I really don't understand.
I wanted to install Ubuntu Server on a headless box I have. The desktop sits right next to it, and adding and removing disks are very easy, so I just created a VirtualBox image for the disk using VBoxManage internalcommands createvmdk -filename ~/phys-disk.vmdk -rawdisk /dev/sdb.
The virtual machine boots just fine, everything works exacty as expected and I install Ubuntu Server 14.04LTS. Networking is configured to Bridged and I can ping the host from the outside. I install openssh-server and I can connect from other devices as well as the host. In other words, everything is fine.
Then I shutdown the VM, remove the disk, insert it into the server and reboot it. It's the only disk connected. After a while, the server starts answering to pings. However, it no longer responds to port 22. When I move it back to the VM host, everything is working again and then back at the server, sshd doesn't reply.
For the life of me, I can't figure out the cause of this. Because the VM host and the server are both directly connected to the same switch. The only thing I can think of, is that sshd somehow refuses to open ports when the NIC's MAC changes, but I can't find any such setting.
I don't believe I've ever encounted this on earlier versions of Ubuntu, but then I'm also not sure if I've ever installed it that way before. Any ideas?